The effect of radiative decay of massive particles on the spectrum of the microwave background radiation

Abstract

The effect of radiative decay of weakly interacting massive particles on the spectrum of the cosmic microwave background radiation is investigated by solving the Kompaneets equation in the expanding universe numerically. By comparing the spectrum obtained by numerical integration with observational data, the constraint on the lifetime of unstable particles is obtained as a function of their mass. We conclude that the lifetime of the radiatively decaying particles with mass m x should satisfy the following inequality; τ 0 < 2 × 10 6[1 + (10 3 eV/m X ) 2] −1 2 s , in the mass range m X < 0.1 MeV.